Asexual Reproduction vs. Sexual Reproduction

Asexual Reproduction One Parent Required Does NOT Require Gametes (sex cells) Offspring produced by cell division. Offspring identical to Parent (Identical DNA) Several Different Types Binary Fission Budding Regeneration/Fragmentation Vegetative Propagation Sporulation

Binary Fission Organisms Divide in Half 2 Identical daughter cells produced. Daughter cells are half the parent’s size. Daughter cells grow and then divide into two new identical cells. This occurs in bacteria.

Budding Small bud grows out of parent cell Two different sized cells made (with identical DNA) Bud breaks off and grows This occurs in yeast and hydra

Regeneration Repair/ grow lost body parts Left over cells divide to make more cells Occurs in Lobsters, starfish, lizards

Fragmentation A single parent breaks into parts that regenerate into whole new individuals.

Vegetative Propagation Occurs only in plants (vegetative). New plants develop from the roots, stems, or leaves of the parent plant.

Sporulation Spore Formation Spores are produced and each spore develops into offspring which are identical to parent Spores are surrounded by a tough coat to help them survive harsh environmental conditions. This occurs in fungi, green algae, molds and non flowering plants (e.g. ferns)

Sexual Reproduction Sexual reproduction is the production of offspring using gametes (sex cells). Requires two parents that each share ½ of the genetic information. Offspring share the characteristics of each parent. The cells of the offspring have two sets of chromosomes (one from each parent), so are diploid. Haploid = half the number of chromosomes. Human haploid cells have 23 chromosomes Diploid= 2 of every chromosome Human diploid cells have 46 chromosomes. Results in offspring that have a variety of traits that are similar to the parents, but not exact copies!

Fertilization Internally (inside) Externally (outside) The egg is fertilized by sperm inside the female Mammals, birds, reptiles, insects, spiders Externally (outside) The egg is fertilized by sperm outside the female The female lays the eggs and then the male fertilizes them. Fish and some amphibians Plants and fungi (pollen and spores)

Pollination pollen grains from the anther are transferred to the stigma by the process of pollination self pollination (plant pollinates its own eggs) cross pollination (pollen from one plant pollinates another plants eggs) flowers are designed to lure insects to help with the pollination process also wind, animals, birds can transport pollen

Some Organisms do Both most plants that produce seeds (sexual reproduction) can also reproduce asexually by things like cuttings or runners this gives them an advantage for survival mosses sponges and hydra

Which is Better? It depends! Asexual Reproduction advantages does not require special cells or a lot of energy can produce offspring quickly in a stable environment creates large, thriving population disadvantages limited ability to adapt face massive die-off if environment changes Sexual Reproduction advantages lots of variation within a species able to live in a variety of environmental settings able to adapt to changes in the environment disadvantages needs time & energy produce small populations